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College Algebra Prerequisite Topics Review. Quick review of basic algebra skills that you should have developed before taking this class 18 problems that are typical of things you should already know how to do . Review of Like Terms.

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## College Algebra Prerequisite Topics Review

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**College Algebra Prerequisite Topics Review**• Quick review of basic algebra skills that you should have developed before taking this class • 18 problems that are typical of things you should already know how to do**Review of Like Terms**• Recall that a term is a constant, a variable, or a product of a constant and variables • Like Terms: terms are called “like terms” if they have exactly the same variables with exactly the same exponents, but may have different coefficients • Example of Like Terms:**Adding and Subtracting Like Terms**• When “like terms” are added or subtracted, the result is a like term and its coefficient is the sum or difference of the coefficients of the other terms • Examples:**Polynomial**• Polynomial – a finite sum of terms • Examples:**Adding and Subtracting Polynomials**• To add or subtract polynomials: • Distribute to get rid of parentheses • Combine like terms • Example:**Problem 1**• Perform the indicated operation: • Answer:**Multiplying Polynomials**• To multiply polynomials: • Get rid of parentheses by multiplying every term of the first by every term of the second using the rules of exponents • Combine like terms • Examples:**Problem2**• Perform the indicated operation: • Answer:**Squaring a Binomial**• To square a binomial means to multiply it by itself • Although a binomial can be squared by foiling it by itself, it is best to memorize a shortcut for squaring a binomial:**Problem3**• Perform the indicated operation: • Answer:**Dividing a Polynomial by a Polynomial**• First write each polynomial in descending powers • If a term of some power is missing, write that term with a zero coefficient • Complete the problem exactly like a long division problem in basic math**Problem4**• Perform the indicated operation: • Answer:**Factoring Polynomials**• To factor a polynomial is to write it as a product of two or more other polynomials, each of which is called a factor • In a sense, factoring is the opposite of multiplying polynomials: We have learned that: (2x – 3)(3x + 5) = 6x2 + x – 15 If we were asked to factor 6x2 + x – 15 we would write it as: (2x – 3)(3x + 5) So we would say that (2x – 3) and (3x + 5) are factors of6x2 + x – 15**Prime Polynomials**• A polynomial is called prime, if it is not 1, and if its only factors are itself and 1 • Just like we learn to identify certain numbers as being prime we will learn to identify certain polynomials as being prime • We will also completely factor polynomials by writing them as a product of prime polynomials**Importance of Factoring**• If you don’t learn to factor polynomials you can’t pass college algebra or more advanced math classes • It is essential that you memorize the following procedures and become proficient in using them**5 Steps in Completely Factoring a Polynomial**(1)Write the polynomial in descending powers of one variable (if there is more than one variable, pick any one you wish) (2) Look at each term of the polynomial to see if every term contains a common factor other than 1, if so, use the distributive property in reverse to place the greatest common factor outside a parentheses and other terms inside parentheses that give a product equal to the original polynomial (3) After factoring out the greatest common factor, look at the new polynomial factors to determine how many terms each one contains (4) Use the method appropriate to the number of terms in the polynomial: 4 or more terms: “Factor by Grouping” 3 terms: PRIME UNLESS they are of the form “ax2 + bx + c”. If of this form, use “Trial and Error FOIL” or “abc Grouping” 2 terms: Always PRIME UNLESS they are: “difference of squares”: a2 – b2 “difference of cubes”: a3 – b3 “sum of cubes”: a3 + b3 In each of these cases factor by a formula (5) Cycle through step 4 as many times as necessary until all factors are “prime”**Factoring the Greatest Common Factor from Polynomials**(Already in descending powers of a variable) 9y5 + y2 y2( ) y2(9y3 + 1) 6x2t + 8xt + 12t 2t( ) 2t(3x2 + 4x + 6)**Factor by Grouping(Used for 4 or more terms)**(1) Group the terms by underlining: If there are exactly 4 terms try: 2 & 2 grouping, 3 & 1 grouping, or 1 & 3 grouping If there are exactly 5 terms try: 3 & 2 grouping, or 2 & 3 grouping**Factoring by Grouping**(2) Factor each underlined group as if it were a factoring problem by itself (3) Now determine if the underlined and factored groups contain a common factor, if they contain a common factor, factor it out if they don’t contain a common factor, try other groupings, if none work, the polynomial is prime (4) Once again count the terms in each of the new polynomial factors and return to step 4.**Example of Factoring by Grouping**Factor: ax + ay + 6x + 6y (1) Group the terms by underlining (start with 2 and 2 grouping): ax + ay + 6x + 6y (2) Factor each underlined group as if it were a factoring problem by itself: a(x + y) + 6(x + y) [notice sign between groups gets carried down]**Factoring by Grouping Example Continued**(3) Now determine if the underlined and factored groups contain a common factor, if they do, factor it out: a(x + y) + 6(x + y) (x + y)(a + 6) ax + ay + 6x + 6y = (x + y)(a + 6) (4) Once again count the terms in each of the new polynomial factors and return to step 4. Each of these polynomial factors contains two terms, return to step 4 to see if these will factor (SINCE WE HAVE NOT YET DISCUSSED FACTORING POLYNOMIALS WITH TWO TERMS WE WILL NOT CONTINUE AT THIS TIME)**Example of Factoring by Grouping**Factor: (1) Group the terms by underlining (Try 2 and 2 grouping): • Factor each underlined group as if it were a factoring problem by itself: [notice sign between groups gets carried down and you have to be careful with this sign]**Factoring by Grouping Example Continued**(3) Now determine if the underlined and factored groups contain a common factor, if they do, factor it out: (4) Once again count the terms in each of the new polynomial factors and return to step 4. Each of these polynomial factors contains two terms, return to step 4 to see if these will factor (AGAIN WE HAVE LEARNED TO FACTOR BINOMIALS YET, SO WE WON’T CONTINUE ON THIS EXAMPLE)**Note on Factoring by Grouping**• It was noted in step 3 of the factor by grouping steps that sometimes the first grouping, or the first arrangement of terms might not result in giving a common factor in each term – in that case other groupings, or other arrangements of terms, must be tried • Only after we have tried all groupings and all arrangement of terms can we determine whether the polynomial is factorable or prime**Try Factoring by GroupingWithout First Rearranging**Factor: (1) Group the terms by underlining (Try 2 and 2): • Factor each underlined group as if it were a factoring problem by itself: .**Now Try Same Problemby Rearranging**Factor: Rearrange: (1) Group the terms by underlining: • Factor each underlined group as if it were a factoring problem by itself: .**Factoring by Grouping Example Continued**(3) Now factor out the common factor: (4) Once again count the terms in each of the new polynomial factors and return to step 4. Each of these polynomial factors contains two terms, return to step 4 to see if these will factor (AGAIN WE TO WAIT UNTIL WE LEARN TO FACTOR BINOMIALS BEFORE WE CAN CONTINUE)**Factoring Trinomials byTrial and Error FOIL(Used for 3 terms**of form ax2 + bx + c) • Given a trinomial if this form, experiment to try to find two binomials that could multiply to give that trinomial • Remember that when two binomials are multiplied: First times First = First Term of Trinomial Outside times Outside + Inside times Inside = Middle Term of Trinomial Last times Last = Last Term of Trinomial**Steps in Using Trial and Error FOIL**• Given a trinomial of the form: • Write two blank parentheses that will each eventually contain a binomial • Use the idea that “first times first = first” to get possible answers for first term of each binomial**Continuing Steps in Trial and Error FOIL**• Given a trinomial of the form: • Next use the idea that “last times last = last” to get possible answers for last term of each binomial**Continuing Steps in Trial and Error FOIL**• Given a trinomial of the form: • Finally use the idea that “Outside times Outside + Inside times Inside = Middle Term of Trinomial” to get the final answer for two binomials that multiply to give the trinomial**Prime Trinomials**• A trinomial is automatically prime if it is not of the form: • However, a trinomial of this form is also prime if all possible combinations of “trial and error FOIL” have been tried, and none have yielded the correct middle term • Example: Why is this prime? • The only possible combinations that give the correct first and last terms are: • Neither gives the correct middle term:**Example of Factoring byTrial and Error FOIL**• Factor: 12x2 + 11x – 5 • Using steps on previous slides, we see all the possibilities that give the correct first and last terms on the left and the result of multiplying them on the right (we are looking for the one that gives the correct middle term): (12x + 1)(x – 5) = 12x2 – 59x – 5 (12x – 1)(x + 5) = 12x2 + 59x – 5 (12x + 5)(x – 1) = 12x2 – 7x – 5 (12x – 5)(x + 1) = 12x2 + 7x – 5 (6x + 1)(2x – 5) = 12x2 – 28x – 5 (6x – 1)(2x + 5) = 12x2 +28x – 5 (6x + 5)(2x – 1) = 12x2 + 4x – 5 (6x – 5)(2x + 1) = 12x2 – 4x – 5 (4x + 1)(3x – 5) = 12x2 – 17x – 5 (4x – 1)(3x + 1) = 12x2 + x – 5 (4x + 5)(3x – 1) = 12x2 +11x – 5 (4x – 5)(3x + 1) = 12x2 -11x – 5**A Second Method of Factoring Trinomials**• While the “Trial and Error FOIL” method can always be used in attempting to factor trinomials, and is usually best when first and last terms have “small coefficients,” there is a second method that is usually best to use when first and last coefficients are “larger” • We call the second method: “abc grouping”**Factoring Trinomials byabc Grouping(Used for 3 terms of form**ax2 + bx + c) • When a polynomial is of this form: ax2 + bx + c • Identify “a”, “b”, and “c” • Multiply “a” and “c” • Find two numbers “m” and “n”, that multiply to give “ac” and add to give “b” (If this can not be done, the polynomial is already prime) • Rewrite polynomial as: ax2 + mx + nx + c • Factor these four terms by 2 and 2 grouping**Example of Factoring byabc Grouping**• Factor: 12x2 + 11x – 5 (1) Identify “a”, “b”, and “c” a = 12, b = 11, c = - 5 (2) Multiply “a” and “c” ac = - 60 (3) Find two numbers “m” and “n”, that multiply to give “ac” and add to give “b” (If this can not be done, the polynomial is already prime) m = 15 and n = - 4, because mn = -60 and m + n = 11 (4) Rewrite as four terms: 12x2 + 15x – 4x – 5 (5) Factor by grouping: 12x2 + 15x – 4x – 5 3x(4x + 5) – 1(4x + 5) (4x + 5)(3x – 1)**Example of Factoring byabc Grouping (with two variables)**• Factor: 35x2 – 12y2 – 13xy 35x2 – 13xy – 12y2 (descending powers of x) (1) Identify “a”, “b”, and “c” (Ignore y variable) a = 35, b = - 13, c = - 12 (2) Multiply “a” and “c” ac = - 420 (3) Find two numbers “m” and “n”, that multiply to give “ac” and add to give “b” (If this can not be done, the polynomial is already prime) m = 15 and n = - 28, because mn = - 420 and m + n = - 13 (4) Rewrite as four terms: 35x2 + 15xy – 28xy – 12y2 (5) Factor by grouping: 35x2 + 15xy – 28xy – 12y2 5x(7x + 3y) – 4y(7x + 3y) (7x + 3y)(5x – 4y)**Factoring Binomials by Formula**• Factor by using formula appropriate for the binomial: “difference of squares”: a2 – b2 = (a – b)(a + b) “difference of cubes”: a3 – b3 = (a – b)(a2 + ab + b2)Trinomial is prime “sum of cubes”: a3 + b3 = (a + b)(a2 – ab + b2)Trinomial is prime • If none of the formulas apply, the binomial is prime BINOMIALS ARE PRIME UNLESS THEY ARE ONE OF THESE**Example of Factoring Binomials**• Factor: 25x2 – 9y2 • Note that this binomial is a difference of squares: (5x)2 – (3y)2 • Using formula gives: (5x – 3y)(5x + 3y)**Example of Factoring Binomials**• Factor: 8x3 – 27 • Note that this is a difference of cubes: (2x)3 – (3)3 • Using formula gives: (2x – 3)(4x2 + 6x + 9)**Example of Factoring Binomials**• Factor: 4x2 + 9 • Note that this is not a difference of squares, difference of cubes, or sum of cubes, therefore it is prime • (4x2 + 9) • To show factoring of a polynomial that is prime, put it inside parentheses**Problem5**• Factor completely: • Answer:**Problem6**• Factor completely: • Answer:**Problem7**• Factor completely: • Answer:**Problem8**• Factor completely: • Answer:**Problem9**• Factor completely: • Answer:**Rational Expression**• A ratio of two polynomials where the denominator is not zero (an “ugly fraction” with a variable in a denominator) • Example:**Reducing Rational Expressions to Lowest Terms**• Completely factor both numerator and denominator • Apply the fundamental principle of fractions: divide out common factors that are found in both the numerator and the denominator**Example of Reducing Rational Expressions to Lowest Terms**• Reduce to lowest terms: • Factor top and bottom: • Divide out common factors to get:

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